Abstract #301556

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JSM 2003 Abstract #301556
Activity Number: 373
Type: Contributed
Date/Time: Wednesday, August 6, 2003 : 10:30 AM to 12:20 PM
Sponsor: Biometrics Section
Abstract - #301556
Title: A Power Comparison of Statistics for Surveillance of Bioterrorism
Author(s): Sylvan Wallenstein*+ and Joseph I. Naus
Companies: Mount Sinai School of Medicine and Rutgers University
Address: 1166 W Laurelton Pkwy., Teaneck, NJ, 07666-2749,
Keywords: scan statistic ; bioterrorism
Abstract:

Two methods for detecting clustering in time t of events that could be associated with bioterrorism are developed and compared. We focus on ongoing evaluations of a specific geographic area, based on a time window w. The statistics are based on either (i) the maximum of functions involving observed and expected numbers of events in (t, t+w), or (ii) the maximum of the ratio of such events (e.g., flu-like symptoms) to a time-varying denominator (e.g., emergency room visits). One class of tests is based on the Generalized Likelihood Ratio Test (GLRT), and the other (tentatively called the S-test) uses an explicit p value that is obtained from a variant of the 'classic' scan statistic. The GLRT can be applied in a broad variety of circumstances and requires simulation; the S-test must be developed anew for each application, but does not require simulation. We derive simple-to-calculate approximations to power for both statistics for pulse alternative in case (i). Based on this formula and simulations for a related case, we suggest that for diseases with strong underlying seasonal components, the tests are sensitive to increases at different times of the year.

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